Adjustable pitch propeller mechanism for airplanes



RPLANES 6 Sheets-Sheet 1 INVENTOR. M677 /'7Ze0 BY I 5 ATTORNEYfi Nov.14, 1944. A. K. MCLEOD ADJUSTABLE PITCH PROPELLER MECHANISM FOR AIOriginal Filed Jan. 6, 1956 ,Nov. 14, 1944. A. K. MCLEOD 2,362,914

ADJUSTABLE PITCH PROPELLER MECHANISM FOR AIRPLANES Original Filed Jan.6, 1936 6 Sheets-Sheet 2 55 so Z4 55 52 lZ/bm rr. 176M BYWM ATTORNEYSNov. 14, 1944. A, McLEOD 2,362,914

ADJUSTABLE PITCH PROPELLER mmcmuxsm FOR AIRPLANES Original Filed Jan. 6,1936 6 Sheeqs-Sheet 3 INVENTOR. N w/0d ATTORNEYS Nov. 14, 1944. A. K. M0500 2,362,914

ADJUSTABLE PITCH PROPELLER MECHANISM FOR AIRPLANES 6 SheetsSheet 4Original Filed Jan. 6, 1936 INVENTFOR.

Y ATTORNEYS Nov. 14, 1944. A. K. M LEOD ADJUSTABLE PIFTCH PROPELLERMECHANISM FOR AIRPLANES Original Filed Jan. 6, 1936 6 Sheets-Sheet 5 VWf/l/ ATTORNEYS Nov. 14, 1944. A. K. McLEoD 2,362,914

ADJUSTABLE PITCH PROPKLLER IEGHANISH. FOR AIRPLANES 6 Sheets-Sheet 6Original Filed Jan. 6. 193a INV ENT OR.

fi/el-f mum BY ,j

ATTORNEYQ details will appear from low. -I describe a preferredembodiment of my lemma-Pa Albert Kenneth McLeod,

Aviation' Pate signor to 2,362,914 H I g V rltornrmn. MECHA: gmsrrron v;.s

Lcs Angcies, Cali1.,as'- I nts, Inc., :Los :Angeles, x

. 1 calif acorporation of California. 1

.Cn'tiridatibhibt; January 6,

application' seriai No. 57,739;

936'.' This application July 27,

' v 193 9 Serial No.-286.940-

This inventionrelates to improvements in an" adjustable pitch propellerm echanism for airplanes.

The objects of this invention are: First, to provide an improvedadjusting means i for the propeller blades.

Second, toprovide'improved control ror'su'ch propeller blades when inaction.

Third, to providej'e'ffective automatic constant speed electriccontrols.

Fourth, to provide in improved counterbalance means able blades ofthepropeller.

Fifth, to provide an improved tachometer such a combination air for theadjustmeans for-such a combination and control.

Sixth, to provide an improved means for 'manualcontrol of the whole'oiyany of the parts,

including the manual adjustment of the propeller blades. 1 t

Further objects pertaining to economies and the description tofolinvention in the followingspecificationand the attached drawings; inwhich:

Fig. 1 is a fragmentary front elevation'of the hub. of a brokenoihpartially section line l of Figs. 2 and 7..

2 is a reduced sectional side elevation view three-blade propeller; withthe blades of the same parts partly in'section through the propellerblade'shank on line 2-2 of Fig. 1.'

Fig. 3 is an enlarged view on the planes of lines 3- -3 of Figs. 1, 4.5,and 9, a part of the view showing the worm gear and the hub parts beingon line 3-3 of Figs. 1, 4, and 9, while the magnet and the manualdriving pinion are onthe plane of line 3-3 of Fig. 5. a a 1 Fig. 4 is adetail sectional view somewhat reduced insize on line 4-4 of Fig. 3,showing the details of the adjusting ring gear means- Fig. 5 is asomewhat tion on lines5-5 of Fig. 3 through the electromagnets, theircoils and the electromagnet casing.

Fig. 6 is an enlarged detail of one of the yieldin section ontheirr'egular detail composite sectional means on line [1- reducedsectional elevaing support pin means for the braking armature assumes inoperation and other the depressible switch member which or for reversingthe propelleras emergency rev quires." p

Fig. 9 is a. reduced front elevation view of the three-blade propeller,part of two of the blades being broken away...- v

Fig. 101s an enlarged detail sectional view on] line 10 o of Fig. 9through one of the propeller blades, there'being added in dotted linesand diagram-the difierent' positions which theblade t details.

]Fig. 11is an enlarged detail sectional view on line H -H of Fig. 9showing details of the propeller counterweight and its divided attachingring, the relation and angle of the propeller blade being shown bydotte'dlines;

Fig. 12 is a detail front elevation view of the tachometer with myattachments.

Fig. 13 is an enlarged detail elevation of the rear face of thetachometer with my attachments} 'Fig. 14 is an elevation view from theleft hand of Fig. 13 showing the tachometer With'my ad justingstopsomitted and the cutaway wall'and I an end view of the'flexible brushmember.

Fig. 15 is an enlarged detail elevation view of permits the flexibleindicating switch member to automatically' move to position.

Fig. 16 isan enlarged elevation view of my adjusting means for adjustingthe rangeof' the tachometer control taken from the right hand of Fig. 12and the left hand of Fig. 13.

Fig. 17 is an enlarged detail sectional elevation view taken centrallythrough the adjusting I! of Figs.- 12, 13, and 16.

Fig. 18 is adetail wiring diagram of the entire electric system showingconventional and simple relays and "circuits therefor. The relays areavailable in many forms, I show two batteries as the simplest.

Fig. 19 is a detail view partly diagrammatic of the manual adjustingmeans comprising the adjustable flexible shaft and pinion with a crankfor the-manual control of the concentric outer rin gear and controllingpinions and adjusting worm gears for the propeller blades. 3

Fig; 20 is a similar diagrammatic view where a simple form of electricstarting motor ismade use of 1 in this connection by 'merely pushingthebuttonof the starter." 1

. The parts will be identified by their numerals of reference which arethe same in all the views. A three-blade propeller is illustrated. l isthe I hub. The hub is counterbored 18 being provided with hub of thepropeller of barrel form. I is the engineshaitwhichissplined at!intcthehubl andhasacoliarl. Theshai'tiprojectsfrosn the nose of theengine I. x

the inner end of the shaft enlarged conical inner end 1 which ilts intocorresponding centering recession the inner endoi. the at l to. receivethe hubnut II which forces conical centering ring ll into acorresponding seat I! in the hub. The nut I, when screwed onto the outerend of the shaft 2, forces the conical members I and ii into the hub andcenters the same eii'ectively on theshaft. Aspringlocking ring llisinthe annular recess M in the projecting end of thehl'ibandlocksthehubnut llinplace. 'I'hlsls good practice in use forattaching the propeller hub. 1

Each propeller blade II is revolubly supported upon ashank l6 (seeFig. 1) which is shouldered and screw threaded at ll into the huh I. The

.splines are machined into the shank II and hub l at the same operation.The propeller blade I! is provided with a journal heating it for thejournaled outer end of the shank I, the bearing a bushing ll. The innerend of the shank "is a journal and is provided withajournalbearing IIwithabushing II inserted into the adjusting thrust collar 22. Theadjusting thrust collar 22 is secured to the inner end of the propellerby the buttress type of screw thread at 23. The a justing collar isprovided with a shoulder 24 and receives the thrust ball bearings 25which are within the propeller socket 26 integral with hub I and held bythe screw thimble 21 threaded into the outer end of the propeller bladesocket I6.

28 is the worm gear adiusting means on the 7 end adjusting collar 22. I!is the worm. which controls gear 28. It is retained by the housing 30which contains-thrust bearings ll, 32 at each end, which are kept inplace by the plugs II, 34, screw threaded into the bearing housingenlargements 35, 35 at the ends of the housing that embrace the ballbearings. The housing II is retained in place by a series of cap screws36, see Figs. 1, 2, and 3 for the details.

The worms 29 are provided with bearing shafts 31 to each of which issecured a pinion I! by suitable keys 4|, indicated by dotted lines inFig. 3. These pinions 39 are disposed between the inner spur gear ring4| and the outer internal threaded gear ring 42, see Fig. 4. Theadjusting ring gears 4| and 42 are supported within the annular housing43, the inner face 44 of which is located by dowel pins 45 on the end ofthe huh I and is secured by screws to the screw plugs 34 which retainthe thrust bearing of the worm 29 in place. The ball bearing ring 46 isfitted securely within the periphery of the housing 43 and is retainedby a screw threaded ring nut 41. An inner ball bearing ring 48 for thering 4| is carried by the spacing sleeve 8 and is clamped in place bythe screw threaded ring 49 which clamps the hearing ring 48 against theinner edge of the housing 43 and assists in clamping and holding thesame in place. The outer ring gear 42 is tempered and hardened at itsperiphery to form the outer member or race or the bail bearing thereforand cooperates with the balls 50 which are retained in a suitable ballring within the bearing ring 45 and the peripheral bearing surface ofthe ring bearing so that the outerring gear is freely rotatable andadjustable within the casing for the pur- Aspacimsleeveliscn pme ofcontrolling the pinions above-mentioned. A shield 43! is provided forprotecting the parts from the elements.

The inner or spur gear 4| is hardened on its inner bearing surface andcooperates with the balls 8| which run in the race within the bearing"ring 48 whereby this inner spur gear readily rotates and is adjustableand in mesh with the These pinions, ring gears, and parts all revolvewith the hub. It is clear that, if the outer ring gear 42 is retarded orstopped in iisrelative movement to the ring 4|, this will cause thepinions 39 to rotate and, by their rotation, they cause the operation ofthe worms 28 and adjust the pitch of the propellers. On the other hand,if the ring spur gear 4| is retarded. it will also have the effect ofrotating the aforesaid pinions but in the opposite direction, causingthe corresponding adjustment of the pitch of the propellers. Ipreferably do the retarding with magnetic brake means, but other meansare available. The worms 29 have a low helix angle and are adjusted onlyby the action shown.

I provide armature rings or steel correspondaforesaid pinions 38.

ing to each of the'ring gears and support them parallel to the axes ofsaid 7 yieldingly held inwardly by coil spring cons on. The internalgear ring 4| is provided with armature ring 52 and the externalinternally-toothed gear ring 42 is provided an armature ring 53. Thearmature ring 53 is provided with an internal oblique flange l4 toothedon its edge for the purpose of hand or independent manipulation,hereafter to be described The armature rings are each supported by a setof spring pins which are all the same, one of them being detailed inFig. 6. The pin 58 is carried in a screw sleeve 56 which is screwed intoa socket bore 51, which sleeve is held adjlw eblv in place by the locknut I. The inner end of the pin is screw-threadon pins which are ringgears and are 4 ed and provided with an adjusting screw nut 59.

K coiled spring 0. is on the axle, the tension of which is varied by thenut 59 which reacts upon the outer end of the spring. The inner end ofthe Spring is bottomed against the screw-threaded sleeve 5.

Corresponding to the armature rings are annular elets ii for the innerring 4| and 81 for the outer ring 42. The housing of each of thesemagnets is a U-shaped annular ring havin grooves, 64, made of pure ironor high grade cast iron or whatever is found to be most eirective asmagnets. These magnets are carried by supports Gill secured to the motorhousing by cap screws 6| The same are provided with annular coils ofwire, the inner and outer 66, constituting the coils of each of saidmagnets. .The cores of the magnet are external to the coils. These coils65 and 66 are, according to the oilicial aircraft requirements. closedcoils extending from one side to the other of the battery or source ofelectric current used. Supported opposite the core of each magnet andwithin the magnet casing are brake rings 61 of non-magnetic material forthe inside and brake rings 68 for the outer magnet. These are rigidlysecured to the shells of the magnets by suitable screws 69 (see Fig. 6and are very accurately spaced from the armature, whereby a very slightexcitation of the coils causes,the armatures to contact with the brakewith a slight pressure, causing retardation in proportion to the currentand to the coeilicient of friction. This structure illustrated isengineered; for direct electrici are,

renti 'Thesa a r I 'altemating current but" would be engineered anddesigned accordingly] On th outer armature ringSS, I form me tensionoblique flange 54 and provide flne gear teeth on the inner edge thereof.I This is for the purpose "of hand or supplemental manipulation of'theexte'rnal ring gear.

JAsmall shaft :18 (see Figs. 7 disposed-in a suitable bearingcarryinga'pinion' 12'adapted tome sh withythege'a'r teeth on e inventioncan" be utilized with loss of'ithefs lal advantag'esf Iri'securing thisresult,'it' is preferredfto make a master blade 7 by 'makin partsreadilyadjustable' and then making the'integral completed master bladefrom the adjusted structure as .a pattern. Tothis the screw-threadedweight is added. The slight adjust ment 'p'o ible by the\s crew-threadedweight "'l9'mak'esitpossible to adjust and accurately theflange'fl. Theshaft Ill is drivenby a'crank 18' connected by a flexible shaft I3:(Fig; 19), the crank projecting ataconvenient place on the instrumentboard or within reach of the pilot in the cockpit. If the engine hasgone dead and the propellers are notrotating, this enables the'pilotybypushing the pinion- 12 into engage-- ment, tocrank the same and turn theouter gear ring sufliciently to adjust the propeller'blades .toytheedgeor feathering position so-that the .propeller will not offer resistanceand will not counterbalance each individual propeller blade by the meanshere illustrated. The blade is madesubstantially correctbya master bladeand this slight variation by the screw adjustment takes care of thecomplete adjustment'of ,the same.

Very slight adjustment of the pitch of ,the blade makes a greatdifference in its action. In Fig.- 10, I have indicated this range byshowing the-blade in cross section, the full lines showing windmill,thus enabling,in the event of a single propellerumachine, the gliding togroundin a much. larger radius, ;and,-in the event: the 'engine-is onein a multiple-engine planeg thesame out of operation so that can be put,effectively 'flying'may' be continued efficiently with-1a part Thismeans is entirely of the propellers in use. independent of the magneticelectric. apparatus.

InF'ig. 20, I have shown,

the shaft 10 and the pinion 12, a small electric starter motor "I!controllediby the usual starter. button. This is largely indicateddiagrammat-- ically and is not detailed becausethe details for suchstarting motor'are well known and well un-.

derstood. 1 By proper energization, this motor can be made to move theouter ring gear relative to the housing and thus vary thepitch of theblades; Y

In an adjustable pitch propeller, the pitch of installed for driving mayopenfsealed switches toone-orthe other of the circuits toone oranotherof the magnets, as

' required, and close the proper opposite circuit.

the propeller is varied by. theadjustmentand this induces adifierentaction upon the propeller, particularly in view of the factthatit israpidly rotating. as well as advancing in' the air. It isarequirement that the propeller be very nicely regulated and balanced bycounterweight .in orderto, avoid undue strains. Clearly, to-calculatethis definitely would call for carefulconsideration of the material ofthe propeller and its and I, therefore, work out this balancing by ruleof thumb. I illustrate and desoribethe preferred procedure under suchcircumstances.

In Fig. 11, I show the counterbalance weight 15 secured on a shank 16 bya divided collar 11 to the round part of the propeller blade, the samebeing suitably clamped thereto, one part carrying the counterweight 15.This is here shown conventionally as a ball but, as a matter of fact, itis of irregular shape to avoid accumulation of ice. The shank radialbore 18. From the center out is a suitably screw-threaded shaft-18lcooperating with the screw-threaded weight 19.1 A gear- I82 is fixed tothe end of the shaft 'l8l and meshes with a driving screw 183.. Thisweight'is adjustable only by special tool or screwdriver operating thescrew I83. This internal support and adjustment is provided to preventdislocation of theparts. which are supported on the propeller arm andsubjected to rapid motion and severe strains. A slight adjustment of.the. weight has a very marked effect on the propeller blade. The weight19 might be form,

16 is provided with a otherwise adjusted with the 76 lwider radius andarea of operation i an'd thereby cause the propeller to 'be adjustedagainst the stop,v which throws the propeller to the'reverse position,gency where the pilotjis required to make a forced landing;By'r'eversing the pitch of the propeliers,"the pilot can'check the speedof the plane and landin a muchsmaller area or field. Also, the circuitmay be thus closed to feather the propellers." In the event the enginethe control circuits'jare thrown outcompletely andit is possible for thepilot, by the, adjusting crank 10', to edge or feather the blades of thepropeller, thereby overcoming their resistance to theiadvance, of theairplane and permitting much ground. If the plane is amu l one, thisadjustment can bepmjade so'far as required when any engine unit fails.

I will'now which the automatic control or tachometer control isaccomplished. The usual construction of tachometer is made use of alongwith attachmerits added thereto. The circuit is closed by a circuitbreaker used in connection with the throttle of the engine. In Fig. 18(see lower left of Fig. 18), I show the throttle lever 83 operating thethrottle control rod 85. I provide a fixed contact 86' and a slidingcontact 81 insulated from the throttle control rod 85. A coil spring 88on the rod causes the same to be held yieldingly in place. Thesecontacts close the circuit when the throttle lever is moved half ortwothirds over and, consequently, the circuit is closed for regulationonly when the throttle is half jay open or open to the extent determinedupen nc forali the lower speeds represented by movement of the throttlebefore this contact is made,

the tachometer control is cut out.

I make additions to the usual construction of tachometer on an airplaneso that the same can beadjusted for thecontrol of the electric currentto the-magnets through the speed ranges which are appropriate to theparticular service required. I

I provide such adjustment that may be set to control the propellerbladesat the most efilcient angle for operation at 1400 R. P. M. I can alsoset the same for the most emcient angle of the This is done in an emergoes dead,

discussthe circuits and means by V 'sition which it takes beingregularly brought into use at or above the range of the rate indicatedup to the high speed limit of the engine. Incidentally, the deviceshould never be set beyond the limit of the high speed of the engine.

I provide controls associated with the moving part of the tachometer.The tachometer is of usuaL-construction with the drive (not illustrated)operating a gear 89 to drive the pinion 90 of the tachometer, therebyoperating its centrifugal governor weights and parts that are connectedto control the indicator hand on the dial and show the speed. I cut outa segment of the wall of the case and secure the flexible contact arm 9|to the hand-carrying part 92 of the tachometer, allowing the end of thearm II with contact head 9| to project through this opening.

I provide a curved segment slideway 93, suitably insulated by blocks 94,95 to carry the adjustable slide block 96 and cooperating contacts I!and 98 (see Fig. 13).

The contact 91 is secured adjustably on the insulated slide block 86 inposition to contact with the contact head 9| on the flexible arm 9|.Contact 88 is pivoted to swing up to permit the flexible arm II withhead 92 to pass up past it. The arm Si is adapted to swing down and passthe pivoted contact 98 against the insulated block 99 below. The pivotedcontact 98 is provided with insulation ill on its face and is pivotedwithin the circuit and held yieldingly out by spring lOi (see detailsparticularly in Figs. 13 to The contact II is connected by a flexibleconducting wire it so that it does not depend upon the pivotal contactfor its electric circuit.

it will be seen that the contact head ll will swing.

uppast the yielding contact 08 without closing the circuit, but on itsreturn will'contact by a wiping contact of the head 9| with the pivotedthe relay magnet III which closes the same and relays to the maincircuit III which is controlled by the throttle lever, as described, andthat this will excite the outer coil 00 which will operate the magneticbrake in that behalf and retard the 42, thereby controlling the pitch ofthe propeller'bladesand increasing the pitch of the propeller by theadvancing edge of the same to secure the stronger action thereof. If thetachometer flexible contact arm 9| swings down, the head ll contacts atand excites the relay circuit I 09 going to the corresponding relaymagnet III, and relays to the main circuit III which leads to the innermagnet coil 85 which serves to rotate the actuating worms in theopposite direction, resulting in decreasing the pitch of the propellerblades. These circuits are connected and both returned to the negativeposts'of the battery.

I also provide a hot wire connection H2 branched at H3 to the outer coil6' controlled by sealed push button switch Ill and branched at I to theinner magnet coil 8! controlled by sealed push button switch H6. Thesepush butcontact 98 and, on the further bending of the flexible arm 9|,it will pass the pivotedcontact "98 and automatically go-out ofcommission and come in engagement with the insulated stop SI.

The insulated slilding block 8! can'be set to any position required onthe tachometer, the po indicated and calibrated in R. P. M. With thestructure illustrated, it can be set from about 1400 R. P. M. to 2500 R.P. M. or more, within the capacity of the highest speed of the engine.The block SI (see Figs. 13 and 14) is adjustable by means of the leverI03 held yieldingly in place by spring Hit. The lever I is provided witha tooth III to engage the notched segment IIII on the outside along theperiphery of the dial face of the tachometer casing. By taking hold ofthe end of the lever I03 which is in the form of a knob, the slide isreleased, the pointer swung to the position required, and the springlever carries the tooth "it into engagement with the notched segmentHi6, holding the same securely in place. The binding posts on theinsulated slide block 98 are connected by very flexible cables into thecircuit so that the slide is adjusted freely back and forth withoutinterfering with the circuit that is connected to the binding post.

By referring to the wiring diagram, particularly Fig. 18, it will beseen that, when the flexible contact arm 0! passes up tothe controlposition and the upper contact 81, the current will be delivered to therelay through circuit ill to ton switches are sealed switches and are tobe used only in-event of emergency. The breaking of the seal requiresthe pilot to make explanation and report.

The outer ring-gear 42 is capable of being manipulated manually. as Ihave explained. It is possible thus to completely control the pitch ofthe blades by such manipulation. The propeller blades may be featheredto prevent windmilling and to reduce the resistance to permit greaterease of cruising with less than all of the engines in a multiple-engineplane or increasing the radius for coasting down in event of an accidentand the stopping of the engine.

.As to the tachometer, I have shown a special construction. The flexiblearm 8| insures a rubbing action for the contact and, consequently,insures most effective action. Likewise, it vibrates and, when nearingone or the other of the contacts, its circuit-closing engagement thereawith is momentary so as to deliver impulses to the corresponding relayand electromagnet. I

have shown one of the stops adjustable and the other stop pivotal,cooperating with the flexible arm, for the special purpose indicated.However, it is clear that the stops being properly placed, the flexiblearm would function without the special construction which facilitatesthe same. The contacts might be made with any moving part of thetachometer which synchronizes with the indicator part.

The use of the flexible switch arm is of importance because the wipingand vibratory action assures an immediate response and eliminates thepombility of welding at the switch due to the passing of current fromthe flexible arm to the contact. This switch is particularly adapted foruse in the relay circuit because it is possible with this switch tohandle a very small amount of current and to provide an eflectivecontact to actuate the magnetic brakes quickly and positively to producethe desired braking effeet. The switch, due to the lack of welding, willrelease quickly and effectively in response to very slight movement ofthe tachometer. In combination with the tilting contact 98, this switchis particularly effective because the automatic control is not put intooperation until the engine of the airplane is up to nearly the desiredspeed. 'I'heflexibleswitcharmcaneasilypassoverthe contact withoutputting the automatic control ing speed. the contacts have provided suchaccurate bearings the 'pinions themselves.- 1 ring alone might tureisrotating into operation when the throttle is opened and. when thethrottle is at the position for operatand switch are positioned for mosteffective cooperative action. When the throttle is retarded, the springar'm'permits' the switch bladeto slide over the contact and theautomatic controlsare effectively put-out of operation forslow oridling'speeds.

The ring gears for'adjusting the propellers I with a special ballbearing with hardened parts which :I" consider desirable in this behalf.It is clear the pinionsto the external and internal gears, the ringswouldnot need tobeprovided' with as they willbecarried-by In this behalfalso, one be made use of by, for instance. connecting the starting motorshown in Fig. to return the same to initial position. By taking time forthe manipulation of the gear rings, it mightbe accomplished by inFig.19, when, suflicint as the pilot could turn the crank'in eitherdirection and make complete adjustments for all purposes, control,feathering, or reverssirable to provide the braking surface with thebrake lining material interposed to secure this braking action. However,it -might be accomplished with a strong enough current without that,with proper fitting of I As to the electromagnetic brake, I find it de-,

could be effectively the crank illustrated of course, one rlngwould beshaft into a I This application a hub; a blade extending j shaftextending parallel of said hub; means s for the current the resultaccomplished without' the The advantages ofthe be omitted in such a Asto the rela' interpositionof relays". relays would, of course,structure.

I have shown direct current. for alternating current as well, mentioned.

the wiring in each instance for The same could be engineered aspreviously I desire-to claim the invention specifically as'wellfasbroadly; v I f I I Y is a continuation of my applicationBeriai-No. 57,739, 'illed January 6, 1936.

I claim as my invention:

1. In an adjustable, pitch combination of a rotatable'member includin IV outward from said hub, means fonpivotally securing said blade to saidhub to turn about an axis of said blade;

toythe rotational axis 7 for journalling said-pinion shaft relative tosaidrotatable member; means for dperatively connecting said pinionshaft'and said blade to translate rotation of said pinion turning of saidblade to vary the pitch thereof; a pinion on said pinion shaft; an

" outer gear comprising a ring gear providing internal teeth meshingwith said gear providing external teeth meshing with said pinion:bearing means the necessity for contact between the parts.

I have shown-a special armature ring The'ring gears themm'agnetic metaland Again, carried by the ringgears. selves might be made 'of pinion; aninner for said outer and irmer "gears; a pair'of brake means forrespectively retarding said inner and outer-gears while said dispensewith these, intervening parts without, I

however, securing the advantages accomplished thereby. V; I A

\ The invention comprehends employment of means for momentarilyretarding the inner and outer gears selectively while the rotatablestructo move the, gears relative to the rotatable structure, whileavoiding. looking or stopping of that gear which is momentarilyretarded, this being accomplished by the two elec- 'hub is rotating andincluding a pair of ring armatures, means for yieldably attaching same'respectively'to said gears and a pair of electromagnetic. meansdisposed respectively adjacent said ring armatures, said electromagneticmeans ring of magnetic material of U-shape providing an annular windingspaceand a winding therein, each ring of magnetic material providing abraking surface contactable with the tromagnetic means respectivelyincluding a ,pairv of normally-open circuits, and a control means formomentarily closing either of the circuits selectively for a period oftime insuflicientito stop either of the p p tarily decelerate the brakedgear with respect to the prevailing speed of the rotatable structure.The invention also comprehends an annular elect-romagnetic element, suchas the annular electromagnet 62, providing a winding and a brakingsurface, with a means for energizing the winding at intervals and ameans for applying a retarding force to the gear means fora shorterperiod-of time than the periodlof time during which the electromagneticelement is energized, this last-named means lncludingfan armatureoperatively'connec'ted to the gear means and spring means resilientlyholding the armature away from the electromagnetic element but exertinga resilient force which is overcome by energization of theelectromagnetic elementand corresponding attraction of the armature toretard thearmature by light frictional contact with the electromagneticelement. The first portion of the period of energization of theelectromagnetic element is used up in an advancing movement of thearmature toward the electromagnetic element so that short periods of retardation can be obtained with longer periods of energization of theelectromagnetic element.

gears but suillcient to momen- I corresponding yieldably-securedarmature when said winding is energized 'thereby' applying a brakingforce to the corresponding gear to rotate said pinion; relay meansproviding sets of contacts; main circuits for respectively connectingsaid sets of contacts in circuit with said windings to energize sameindividually; a tachometer providing means movable in response to therotational speed of said hub and a flexible switch blade driven thereby,said tachometer providing a movable part; a pair of contacts mounted onsaid movable part to be moved together relative to said flexible switchblade and disposed in the normal path of movement of said blade, saidflexible switch blade flexing to pass one of said contacts in movinginto and from an intermediate position therebetween in which it canelectrically contact each of said contacts individually-in responserespectively to an increase and decrease in the rotational speed of saidhub; circuits. connectin s id contacts and said flexible blade to saidrelay means to energize one of said windings when said flexible switchblade electrically engages one of said contacts-and to energize theother of said .windings when said flexible switch blade engages theother one of said contacts; and insulating means on that one of saidcontacts first reached by said flexible switch blade when the speed ofsaid hub increases for preventing electrical contact therebetweenuntilsaid switch blade assumes said inter-mediate position.

, propeller adaptedto be coupled with the shaft of an: engine, the

a pinion 2. In combination: a variable-pitch propeller; pitch varyingmeans for varying the pitch of said propeller while rotating andincluding two electric circuits and means responsive to the energizationof one circuit to increase the pitch andmeans responsive to theenergization of the other peller speed, and means for automaticallypreventing energisation of either of said circuits during movement ofsaid circuit-energizing contact from said end position at one side ofboth the contacts to said intermediate position between the contactswhereby said circuit-energiaing contact is inoperative to control thepitch of said propeller until it assumes said intermediate position.

3. In combination: a variable-pitch propeller; pitch varying mean forvarying the pitch of said propeller while rotating and including twoelectric circuits and means responsive to the energization of onecircuit to increase the-pitch and means responsive to the energizationof the other. circuit to decrease the pitch; and means for selectivelyenergizing said circuits, said means including av tachometer providing a-movable member which advances as the speed of said propeller increases,a flexible blade operatively connected to said movable member to advancefrom a low-speed position to a higher-speed position as said movablemember advances. flrst and second contacts spaced from and insulatedfrom 40 each other and positioned in the path of travel of said flexibleblade, means for electrically connecting said flexible blade and one ofsaid contacts in one of said circuits and for electrically connectingsaid flexible blade said contacts in the other oi said circuits toenergize said circuits selectively in response to electrical contactbetween said flexible blade and speed of said engine constant at adesired value within a few revolutions per minute irrespective ofadjustment of said manually-adjustable means within a normal range oipower outputs. this means including a variable-pitch propeller driven bysaid engine. pitch-varying n :chanism rotating with said propeller,electric means for operating said pitch-varying mechanismand including apair of control circuits adapted when selectively energized to increaseand decrease re-' spectively the pitch of said propeller, control meansindependent of adjustment of said manwilly-adjustable 'means within saidnormal range oi power outputs for selectively energizing said controlcircuits in response to a deviation of engine speed from a desired valueto increase the pitch 01 said propeller when the speed of said engineincreases slightly and to decrease the pitch of said propeller when thespeed 0! said engine decreases slightly thereby maintaining said speedconstant within a few revolutions per minute, and automatic means forrendering said control means inoperative to actuate said electric meansuntil the speed of said engine reaches said desired value.

6. A combination as deflned in claim 5 including as an additional meansa switch means electrically connected to said control circuits to rendersame inoperative when said switch means is and the other or a said hubto turn about an said flrst and second contacts, and means for yieldablyand movably mounting that one of said contacts which is flrst reached bysaid flexible blade in moving from said low-speed position to saidhigher-speed position to permit said flexible blade to displace said oneof said contacts from its path of travel in moving into an intermediateposition between said contacts, said blade flexing in moving from saidintermediate position to permit passage thereof beyond said one of saidcontacts in returning to its said low-speed position.

4. A combination as defined in claim 3 in which the yieldably-mountedcontact includes an insulating member contactable by said flexible bladein moving from said low-speed position toward its position intermediatesaid contacts whereby said contact is displaced from the path oi travelof said flexible blade by contact between said blade and said insulatingmember thus preventing electrical contact between the flexible blade andthe yieldably-mounted contact until said blade assumes its intermediateposition between said contacts.

5. In combination with an engine: manuallyadiustabie means for changingthe power output oi said engine;

and means for maintaining the 16 a momentary in inoperative position-andto render same operative when said switch means is in operativeposltion, and means operatively connecting said switch means and saidmanually-adjustable means for maintaining said switch means in saidinoperative position when said manually-adjustable means is positionedbelow said normal range and for moving said switch means to operativeposition when said manually-adjustable means is moved to a positionwithin said normal range.

7. In an adjustable pitch propeller adaptedtobecoupledwiththeshaitoianengine,the combination 0!: a rotatablestructure including a hub; a blade extending outward from said hub;means for pivotally securing said blade to axis of said blade; an outergear comprising an internally-toothed gear ring concentric with therotational axis of said hub; bearing means for journalling said outergear for rotation about said rotational axis of said hub; an inner gearexternallytoothed and concentric with the axis of rotation oi said hub;bearing means for Journalling said inner gear for rotation about saidrotational both said inner and outer gears; a pinion shaft carrying saidpinion; means for iournalling said pinion shaft relative to saidrotatable structure to rotate about its own axis at a position spacedirom the axis of rotation of said hub; means operatively connecting saidpinion shaft to said propeller blade to turn same in proportion to theangular movement of said pinion: and annular armature for each of saidgears: means for respectively mounting said armatures relative to saidgears and including resilient means for biasing said armatures towardtheir respective gears; a braking ring disposed adjacent each armaturebut spaced very slightly therefrom when said resilient means retractsaid armatures but being ccntactable by said armatures in an annularzone oi contact upon overcoming the biasing force; and means formomentarily slapping either armature against its braking ring and forquickly releasing it thereby imparting retarding force to the gearassoaxis of said hub: a pinion meshing with ciated therewith'without'means, including an annular electromagnetic for a period of slappingcontactbetween tardation being.

including switch means 7 contacts, a third contact adapted. to, be.positational speed of said ,8. In an adjustable pitch propeller adaptedto an engine, the com-- stopping thereof. said means associatedrespectively with each braking ring and means for momentarily andselectively energizing said electromagnetic means time insufllcienttostop the corresponding armature and gear but sufflcient tomomentarilydecelerate-this gear iwith respect to the rotatablestructure through amomentary the corresponding armature and braking ring,

sumcient to :slightly change the .said last- -na'med means providing twospaced pitch of .the propeller,

this -momentary retioned between said 1 two spaced contacts, means z foroperatively connecting said third contact and goneofsaidspacedcontactsto oneof said electromagnetic means andforoperatively connecting said third contact and the other of saidspaced contacts to the other 'of means, a flexible arm carrying saidthird contact -at-an* outer end thereof, "means for 'pivotallymountlngthe other endofi said arm whereby said third contact may swinginto contact with said electromagnetic either of said spacedcontactsank! means for moving said arm which is on said pivotallymounted means in response to deviations of" rohub from a desired value.

be coupled with'the shaft of bination of a rotatable structure includinga hub; a blade extending outward from said hub; means for pivotallysecuring said; bladeto said hub to turn about an axis of said blade; an

to turn same 'inproportion to the angular move-,

outer gear comprising an internally-toothed a ear ring concentric withthe rotational axis of said hub; bearing means for joumalling said outergear 'for rotation about said rotational axis of said hub; an inner gearextemallytoothed andconcentric with the rotational axis of said hub;bearing means for joumalling said inner gear for rotation about saidrotational axis of said hub; a pinion meshing withboth said inner andouter gears; a pinion shaft carrying said pinion; means for joumallingsaid pinion shaft relative to said rotatable structure to rotate aboutits own axis ata position spaced from the axis of rotation of saidconnecting said pinion shaft to said propeller blade to turn same inproportion to the angular movement of said pinion; and means formomentarily retarding said inner and outer gears selectively while saidrotatable structureis rotating to move said gears relative' to'said'rotatable structure while avoidinglocking or stopping of that gear whichis momentarily'retarded,

said means including a pair of electromagnetic associated. with said"inner braking the, motion thereof, each electromagnetic means includingan armature connected to one of said innerand outer gears, anelectromagnet for attracting said armature, and a resilient meansbiasing said armature and said electromagnet away from each other,energization of said :electromagnet exert-'- ing suflicient attractionbetween said armature and said electromagnet 'to overcome the biasingforce of said resilient means, said electromagmeans respectively andouter gears for netic means including a pair of circuits nor-a mallyopen but acting when closed to "brake said inner and outer gearsselectively, and a control means for rapidly making and breaking eitherof said circuits selectively in response to a deviationin propellerspeed from a. desired value, the

hub; means operatively' riod of time between including eachmaking andsubse-. uent' breaking being insumcient to stop either of said gears butsuflicient to momentarily decelerate the braked gear with respect to,the prevailing speed of said rotatable structure thereby. momentarilyretarding it tochange the pitch of said propeller. 1

' 9. In an adjustable pitch propeller adaptedto be coupled with theshaft of an engine, the coin-:-

bination of; a rotatable structure including a hub; a bladeextendingoutward from saidhub; means; for pivot-ally securing said bladeto said hub to turn about an axis of said blade; an outer-gearcomprising aninternally-toothed gear ring concentric with the.rotational axis of said hub; bearing means for "joumalling said outergear for rotation about said rotational axis of saidhub; an innergearexternally-toothed and concentricwith the axis of rotation of saidhub;

bearing means for 'journalling-said inner gear for-rot'ation about saidrotational'axis of said hub; a pinion meshing with both said inner andouter gears; a pinion shaft carrying said pinion; means for joumallingsaid pinion shaft relative to said rotatable structure to rotate aboutits own axis at a position spaced from the axis of rotation ofsaid-hub;v means operatively c'onlne ctin'g' said pinion shaft to saidpropeller bl'ade each of said gears; means for respectively mountingsaid armatures relative to said gears and including resilient means forbiasing said armatures toward their respective gears; a' braking ringdisposed adjacent each armature but spaced very slightly'therefrom whensaid resilient means retract said armatures but being contactable bysaid 'armatures in an annular zone ot contact upon overcoming of thebiasing force: and means for momentarily v slapping either armatureagainst its braking ring and for quickly releasing itthereby imparting amomentary retarding force to the gear associated therewithwithoutstopping thereof, said means I an annular electromagnetic meansas* sociated respectively with each braking ring and means responsive.to changes in speed of said propeller for momentarily and selectivelyenergizing said electromagnetic means for a period of which saidlast-named means includes a switch means adapted when in one position'tosend current toone ofsaid electromagnetic means and when in anotherposition to'send current .to the other of said electromagnetic -means,and impulse-creating means responsive to change in rotational speed ofsaid hub for adjusting said switch means to send a momentary current tothat one of said electromagnetic means effective in changing the pitch'of said propeller in a direction to counteract said slight change inengine speed.

v 11. In an adjustable pitch propeller adapted to be closely coupledwith the shaft of an engine, the combinationof: a rotatable structureincluding a hub and an annular housing, said housing "providing. anoutward-extending wall a slight and a peripheral wall extendingfrom saidoutward-extending wall in a direction away from said hub; a stationaryplate extending outward from the axis of rotation oi said hub to aposition near said peripheral wall of said housing to cooperatetherewith and with said outwardextending wall in defining asubstantially closed annular chamber around the axis of rotation of saidhub, saidv chamber being much larger in a plane normal to said axis ofrotation than in a direction parallel to said axis of rotation; an innerexternally-toothed gear in said annular chamber, said inner gear lyingin a plane perpendicular to said axis of rotation and normally rotatingwith said rotatable structure; bearing means for freely journalling saidinner gear about said rotational axis of said hub; an outerinternally-toothed gear comprising a gear ring with an outer peripherysomewhat smaller than said peripheral wall of said housing, said outergear normally rotating with said rotatable structure and lying in saidplane perpendicular to said axis of rotation, said inner gear lyingwithin said outer gear; a bearing means disposed between said peripheryof said ring gear I and said peripheral wall of said housing to freelyjournal said gear coaxially with respect to said rotational axis of saidhub; an externallytoothed pinion positioned" in said annular chamber insaid plane perpendicular to said axis and meshing with both said innerand outer gears, said inner and outer gears -being disposed radiallywith respect to said pinion; a rotatable pinion shaft towhich saidpinion is secured and extending parallel to but spaced from saidrotational axis of said hub; means for journalling said pinion shaftwith respect to said rotatable structure; a propeller blade extendingoutward from said hub; means for pivotally securing said propeller bladeto said hub to turn about the axis of said blade; means for operativelyconnecting said blade and said pinion shaft to turn said pinion and saidblade simultaneously through proportional angles; an electromagneticmeans including inner and outer windings, inner and outerelectromagnetic cores respectively partially encompassing said inner andouter windings and disposed in a plane parallel to but spaced a shortdistance from said first-named plane perpendicular to said axis. twospaced electrical contacts electrically connected respectively to saidwindings, and a third electrical contact movable in response to changesin propeller speed from a desired value to electrically contact said twospaced contacts selectively to energize said windings selectively; and

means for respectively retarding the normal rotation of said inner andouter gears with respect to said rotatable structure upon energizationof said inner and outer windings.

12. In an adjustable pitch propeller including pivoted blade means, anarmature normally rotating with said propeller and gear means forturning said blade means in proportion to a relative motion between saidarmature and said pro eller, the combination oi: an electromagneticelement adjacent said armtaure and cooperating therewith in defining aflux gap; means for resiliently mounting said armature for movementtoward said electromagnetic element by electromagnetic attraction todecrease the size of said flux gap to such extent that said armaturecomes into contact with said electromagnetic element when saidelectromagnetic element is energized to create a retarding force 011said armature to slow this armature with respect to said propeller;circuit means for energizing said electromagnetic element; and means forrapidly making and breaking said circuit means in response to avchangein the speed of said propeller from a desired value for retuming thepropeller speed to such desired value, said last-named means includingmeans for making and breaking said circuit means at such rate as tocreate a plurality of rapidly recurring electric impulses, each of suchshort duration that application thereof to said electromagnetic elementwill momentarily retard but not stop the rotation of said armature.

13. In an adjustable pitch propeller including pivoted blade means, anarmature normally rotating with said propeller and gear means forturning said bladein proportion toa relative rotation between saidarmature and said propeller, the combination of: an electromagneticmeans adjacent said armature; for resiliently mounting said armature topermit resilient movement thereof toward and into braking contact withsaid electromagnetic means when said electromagnetic means is energized,thus-creating a retarding force on said armature to slow this armaturewith respect to said propeller; and means for energizing saidelectromagnetic means to move said armature against the actionof saidyielding means and into brief slapping relationship with saidelectromagnetic means to change the pitch of said blade means,

said means deenergizing said electromagnetic I means before stopping ofsaid armature can take place, said yielding means being biased to urgesaid armature away from said electromagnetic means to delay contact ofthe armature with the electromagnetic means when the electromagneticmeans is energized and thereby cause the periods ture by of contact tobe substantially shorter than the periods of electromagneticenergization, said means for energizing said electromagnetic meansincluding a circuit providing two spaced contacts and a third contactfor selectively engaging said spaced contacts in response to a deviationin propeller speed from a desired value.

14. In an adjustable pitch propeller including the combination of: gearmeans normally rotating with said propeller; means for operativelyconnecting said gear means to said blade means in such manner thatretardation of said gear means with respect to said propeller willchange the pitch of said blade means; an annular electromagnetic elementincluding a winding; connected to said winding; means responsive to achange in propeller speed from a desired value for energizing saidwinding at intervals; and means for applying a retarding force to saidgear means for a shorter period of time than the period of time duringwhich said electromagnetic element is energized, said means including anarmature operatively connected to said gear means, and spring meansresiliently holding said armature away from said annular electromagneticelement but exerting a resilient force which is overcome by energizationof said electromagnetic element and corresponding attraction of saidarmature to retard said armalight frictional contact with saidelectromagnetic element, the first portion of the period of energizationof the electromagnetic element being used up in an advancing movementarmature toward said electromagnetic element in opposition to saidspring means so yielding means circuit means electrically blade means,the combination of:

that short periods of retardation can be obtained with longer periods ofenergization of said electromagnetic element.

15. In an adjustable pitch propeller adapted to be driven by an engineand including pivoted blade means, the combination of: a magnet housingadapted to be secured to said engine at a position between the engineand said propeller, said magnet housing including inner and outerelectromagnetic elements; gear means rotatable with said propeller andoperatively connected to said blade means to change the pitch thereof;inner and outer ring gears operatively connected to said gear means andnormally rotating with said propeller; inner and outer armaturesrespectively adjacent said inner and outer electromagnetic elements;means for securing said armatures respectively to said inner and outerring gears, said means including spring means normally retracting saidarmatures from contact with said electromagnetic elements whereby duringnormal rotation of said propeller said armatures are spaced from saidelectromagnetic elements; and means for selectively energizing saidelectromagnetic elements to draw said armatures into frictionalengagement therewith to retard selectively the rotation of saidarmatures with respect to said propeller without immobilization of same,said means for selectively energizing said electromagnetic elementscomprising two spaced electrical contacts respectively connected to saidelectromagnetic elements, a third contact movable to selectively engagesaid spaced contacts to selectively energize said electromagneticelements, and means for moving said third contact into its selectiveengagement with said spaced contacts in response to a deviation inpropeller speed from a desired value.

16. In an adjustable pitch propeller adapted to be driven by an engineand including pivoted blade means, the combination of: a magnet housingadapted to be secured to said engine at a position between the saidmagnet housingincluding inner and outer electromagnetic elements; gearmeans rotatable with said propeller and operatively connected to saidblade means to change the pitch thereof inner and outer ring gearsoperatively connected to said gear means and normally rotating with saidpropeller; inner and outer armatures respectively adjacent said innerand outer electromagnetic elements; means for securing said armaturesrespectively to said inner and outer ring gears, said means includinspring means normally retracting said armatures from contact with saidelectromagnetic elements whereby during normal rotation of saidpropeller said armatures are spaced from said electromagnetic elements;and means for selectively energizing said electromagnetic elements todraw said armatures into frictional engagement therewith to retardselectively the rotation 01' said armatures with respect to saidpropeller without immobilization of same, said last-named meansincluding circuit means respectively connected to said electromagneticmeans, relays providing electrical contacts respectively in said circuitmeans, and means for selectively controlling the operation of saidrelays in response to a deviation oi engine speed from a desired value.17. In an adjustable pitch propeller ada ted to be driven by an engineand including pivoted a magnet housing adapted to be secured to saidengine at a pysition between the engine and said pro-v engine and saidpropeller,.

peller, said magnet housing including inner and outer electromagneticelements; gear means rotatable with said propeller and operativelyconnected to said blade means to change the pitch thereof; inner andouter ring gears operatively connected to'said gear means and normallyrotating with said propeller; inner and outer armatures respectivelyadjacent said inner and outer electromagnetic elements; means forsecuring said armatures respectively to saidinner and outer ring gears,said means including spring means normally retracting said armaturesfrom contact with said electromagnetic elements whereby during normalrotation of said propeller said armatures are spaced from saidelectromagnetic elements; and means for selectively energizing saidelectromagnetic elements to draw said armatures into frictionalengagement therewith to retard selectively the rotation of saidarmatures with respect to said propeller without immobilization of same,said last-named means including circuit means respectively connected tosaid electromagnetic means, relays providing electrical contactsrespectively in said circuit means, and manually operable switch meansrespectively in said circuit means for selectively controlling theenergization of said electromagnetic means.

18. In an adjustable pitch propeller including blade means pivoted in ahousing, the combination of: gear means normally rotating with saidhousing; an annular armature associated with said gear means to rotatetherewith, said armature providing a braking surface; means foroperatively connecting said gear means to said blade means in suchmanner that retardation of said armature and gear means with respect tosaid housing will change the pitch of said blademeans; an annularelectromagnetic element including a winding and a braking surface;mounting means for mounting said electromagnetic element and saidarmature for relative movement therebetween from a normal spacedposition in which said braking surfaces are spaced from each other to abraking position in which said braking surfaces are in contact with eachother, said mounting means including resilient means exerting abiasingi'orce tending to separate said braking surfaces, energization ofsaid electromagnetic element exerting an attractive force between saidelectromagnetic element and said armature sufllcient to overcome saidbiasing force to bring said braking surfacesinto braking engagement witheach other to retard the rotation of said armature and said gear meanswith respect to said housing; circuit means for energizing said windingof said electromagnetic element; and means for rapidly making andbreaking said circuit means in response to a change in the speed of saidpropeller from a desired value for returnin the propeller speed to suchdesired value, said last-named means including meansfor making andbreaking said circuit means at such rate as to create a plurality ofrapidly recurring electric impulses, each of such short duration thatapplication thereof to said electromagnetic element will momentarilyretard but not s p the rotation of said armature whereby said armatureis moved relative to said housing by repeated application of suchmomentary retardations to change the pitch of said blade means to thedegree necessary to return the propeller speed to the desired value.

, ALBERT KENNETH McLEOD.

